preload a smaller resolution fullscreen image first

app/src/main/kotlin/com/simplemobiletools/gallery/fragments/PhotoFragment.kt

@@ -240,9 +240,10 @@ class PhotoFragment : ViewPagerFragment() {
             Picasso.get()
                     .load(File(medium.path))
                     .centerInside()
-                    .fit()
+                    .resize(ViewPagerActivity.screenWidth / 2, ViewPagerActivity.screenHeight / 2)
                     .into(view.photo_view, object : Callback {
                         override fun onSuccess() {
+                            view.photo_view.isZoomable = false
                             if (isFragmentVisible) {
                                 scheduleZoomableView()
                             }

app/src/main/res/layout/pager_photo_item.xml

@@ -9,8 +9,7 @@
     <com.github.chrisbanes.photoview.PhotoView
         android:id="@+id/photo_view"
         android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        android:scaleType="fitCenter"/>
+        android:layout_height="match_parent"/>
 
     <com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView
         android:id="@+id/subsampling_view"